ISUOG Basic Training - International Society of Ultrasound ... · PDF file(Gall bladder to right of UV) S DAo ... 5.Lemon sign 6.Cystic hygroma ... Oligohydramnios: Causes Ultrasound

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ISUOG Basic Training

Distinguishing Between Normal and Abnormal Appearances

of the Fetal Anatomy

Reem S. Abu-Rustum, Lebanon

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Learning Objective

At the end of the lecture you will be able to:

• Compare the differences between the ultrasound appearances of

normal fetal anatomy and of the more common structural fetal

abnormalities.

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Key Questions • Which abnormalities can be excluded by obtaining normal HC and AC

sections in the 2nd or 3rd trimester fetus?

• What are principal differences in ultrasound appearances between a

structurally normal fetus and a fetus with open spina bifida?

• How can the AC section be used to exclude the most common abdominal

wall and gastrointestinal defects?

• What are the typical ultrasound features of lower urinary tract obstruction?


Key Anatomic Planes


Scanning Planes


Scanning Planes


Scanning Planes


Image Orientation

ANTERIOR

POSTERIOR

RIGHT LEFT


Image Orientation

ANTERIOR

POSTERIOR

Cephalad Caudad


Determining Fetal Lie Ant

Post

Maternal R Maternal L


Key Features of HC Section


Key Features of HC Section

1. Midline (falx cerebri)

2. Cavum septum pellucidum

3. Rugby football shape, rounded

at back, more pointed at front

4. Skull contour regular

5. Posterior horn <10.0mm

6. Anterior horn(s) slit-like

CSP

T

T

Falx Lateral Ventricle

3V

*


Measure BPD & HC


Posterior Fossa

*

Cerebellum

T

T

Falx


Key Features of AC Section


Key Features of AC Section

1. Short length of umbilical vein,

opposite spine

2. Single stomach ‘bubble’, on left side

3. Remaining echotexture homogeneous

4. (Gall bladder to right of UV)

DAo S

Sp UV

*

*


Measure AC


Schematic adapted from Abuhamad & Chaoui. Practical Guide to Fetal Echocardiography: Normal and Abnormal Hearts. 2nd Edition

L

Establishing Situs


Establishing Situs


First Establish Fetal Position


4 Chamber View

• Easy view to obtain

• No specialized skill needed

• Obtainable in all fetal positions

• Rules out 60% CHD

• Easy slide up from AC with full rib

• Starting point for the sweep


4 Chamber View – Normal Appearance

• Right ventricle is the most anterior, below the sternum

• Left atrium is closest to the spine and the most central structure in the chest

• Tricuspid valve is more apical than the mitral valve

• Flap of the foramen ovale is in the left atrium

• Moderator band is in the right ventricle

• Crux seen

R L

Sp

DAo


Kidneys – Normal Appearance


Kidneys – Normal Appearance

• Lateral to spine

• Posterior to stomach

• Normal renal tissue similar echogenicity

to bowel, liver etc

• (Coronal view allows easier comparison)

• Cortex homogenous echopattern

• Renal pelvis, centrally positioned, <7.0mm

AP

Sp

* *


Cord Insertion – Normal Appearance

1. Slide inferiorly from AC

to sacrum

2. Maintain cross

sectional approach

3. Cord inserts superior

to bladder


Bladder – Normal Appearance

• Central position in fetal pelvis

• Anterior to rectum

• Thin walled

• No internal content

• Size varies (~30 minute cycle)

• Umbilical artery on each side

*


Key Features to Measure FL


Key Features of Amniotic Fluid


Axial Anatomic Planes


Normal or Abnormal Appearances?

Skull

1.Brain, level of ventricles

2.Brain, post fossa

3.Chest – 4 chamber view

4.Abdomen – stomach

5.Cord insertion/abdominal wall

6.Kidneys and bladder

7.Amniotic fluid

8.Size and relative size



1.Skull


3.Brain, post fossa





8.Amniotic fluid



Finding the HC - Shape

1.Dolichocephaly

2.Brachycephaly

3.Anencephaly

4.Encephalocele

5.Lemon sign

6.Cystic hygroma

7.Craniocynostosis


Dolichocephaly

Schematic adapted from: http://breechbirth.org.uk/2014/04/dolichocephaly-understanding-breech-head-molding/


Brachycephaly


Anencephaly


Encephalocele


Lemon Sign


Cystic Hygroma


Craniocynostosis



1.Skull


3.Brain, post fossa





8.Amniotic fluid



Finding the HC – Intracranial Structures

1.Ventriculomegaly

2.Holoprosencephaly


Ventriculomegly


Holoprosencephaly


Finding the Posterior Fossa – Intracranial

Structures

1.Banana sign

2.Vermian agenesis


Banana Sign


Vermian Agenesis


The Spine


Open Spina Bifida Typical Appearances

normal appearances

abnormal appearances



1.Skull


3.Brain, post fossa





8.Amniotic fluid



Finding the 4 Chamber View

1.Situs abnormalities

2.Ectopia cordis

3.Univentricle

4.AV canal

5.CDH


Abnormal Situs


Ectopia Cordis


Univentricle


R

L

Loss of Off-Set

Atrioventricular Septal Defect


R

L

H

S

Loss Off-Set R

L

H S

Congenital Diaphragmatic Hernia



1.Skull


3.Brain, post fossa





8.Amniotic fluid



Finding the AC

1. Establishing situs

2. Absent stomach: esophageal atrsia

3. Double bubble: duodenal atresia


Establishing Situs


Absent Stomach

15 Mins Later


Absent Stomach


Double Bubble Sign



1.Skull


3.Brain, post fossa





8.Amniotic fluid



Cord Insertion/Abdominal Wall

1.Normal gut herniation

2.Omphalocele

3.Gastroschisis


Normal Gut Herniation

Fetuses have exompholos at 9-10 weeks that resolves by 12 weeks


Omphalocele

Abnormal cord insertion

• cord inserts into apex of defect

• contains liver +/- bowel etc

• membrane covered


Gastroschisis

Normal cord insertion

• defect below and to right of cord

insertion

• contains bowel only

• free floating



1.Skull


3.Brain, post fossa





8.Amniotic fluid



Kidneys and Bladder


Kidneys and Bladder

1.Renal agenesis

2.Hydronephrosis

3.Bladder outlet obstruction


Urinary Tract Obstruction

1. Appearances dependent on

• site of obstruction

• unilateral or bilateral

2. Amniotic fluid volume

• oligo/anhydramnios – bilateral

and/or low

• normal fluid - unilateral


Renal Agenesis


Hydronephrosis


Bladder Outlet Obstruction


Bladder Outlet Obstruction



1.Skull


3.Brain, post fossa





8.Amniotic fluid



Oligohydramnios: Causes

Ultrasound in Obstetrics & Gynecology: A Practical Approach. Abuhamad et al 2014


Polyhydramnios: Causes

Ultrasound in Obstetrics & Gynecology: A Practical Approach. Abuhamad et al 2014


Normal or abnormal appearances?

1.Skull


3.Brain, post fossa





8.Amniotic fluid



Size and Relative Size


Key points

1. The key to identifying abnormalities is understanding the range of

normal appearances at differing gestations

2. It is important to develop a consistent approach to each scan, rather

than scanning randomly

3. Find the long axis of the fetus first and assess the appearances


Key points

4. Then assess the fetal anatomy in cross section starting with the

head, assess skull and intracranial anatomy, measure the HC

5. Slide through the chest to the abdomen, assess situs, chest

contents and upper abdomen, measure AC

6. Find FL by continuing to slide through lower abdomen and pelvis,

assess abdominal wall, cord insertion, kidneys, bladder, spine and

skin covering


Conclusions

Distinguishing between normal and abnormal ultrasound appearances

requires:

• The development of a consistent scanning technique

• Paying rigorous attention to the quality of sections obtained

• Understanding how to manipulate the probe to improve poor

sections

• Appreciating how the range of normal appearances, and therefore

potentially abnormal appearances, changes with gestation

Documents

ISUOG Basic Training - International Society of Ultrasound ... · PDF file(Gall bladder to right of UV) S DAo ... 5.Lemon sign 6.Cystic hygroma ... Oligohydramnios: Causes Ultrasound